Fluorinated oxetane derivatives and production process thereof

ABSTRACT

A process for preparing compounds of formula (I) comprising radical addition of RfI to 3-(allyloxy)methyl-3-alkyloxetane (1) wherein R is C 1-3  alkyl and Rf is C 1-18  linear or branched fluoroalkyl.                    
     The compounds of formula (I) are useful as intermediates for preparing various fluorine-containing functional materials.

This application is a 371 of PCT/JP01/01939 filed on Mar. 13, 2001.

TECHNICAL FIELD

The present invention relates to oxetane derivatives having afluorine-containing substituent on the side chain, and a productionprocess thereof. The oxetane derivatives having a fluorine-containingsubstituent on the side chain are useful as intermediates for preparingvarious fluorine-containing functional materials.

BACKGROUND ART

A known method for synthesizing 3-fluoroalkoxymethyl-3-alkyloxetane is,for example, condensation of 3-bromomethyl-3-methyloxetane using afluoroalkyl alcohol and an alkali (Japanese Unexamined PatentPublication No. 500422/1999). However, this method requires the use ofexpensive 3-bromomethyl-3-methyloxetane. In addition, there are somecases in which fluoroalkyl alcohols are not available. Therefore, thedevelopment of a more general-purpose synthetic method has been desired.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for preparing3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane.

Another object is to provide precursors thereof, i.e.,3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane and3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, and processes fortheir production.

The present inventors carried out experiments using the known compound3-alkyl-3-(allyloxy)methyloxetane as a starting compound and found thatradical addition of fluorinated alkane iodide to this compound canproduce 3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, which isan important intermediate in the preparation of oxetane compounds havinga fluorine-containing substituent at the 3-position. The inventorsfurther discovered that3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane can be convertedinto 3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane under basicconditions, and that the resulting3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane can further be convertedinto 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane through a reductionreaction.

The features of the invention are shown in the following Scheme 1:

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.

The compound of formula (II) usually consists mainly of a trans isomer(E isomer) but may be a mixture of trans and cis isomers (E and Zisomers). In the invention, the compound of formula (II) is convertedinto the desired compound of formula (III) through the followingreduction reaction.

The C₁₋₃ alkyl represented by R is methyl, ethyl, n-propyl or isopropy,preferably methyl or ethyl, more preferably methyl.

Rf is a C₁₋₁₈ linear or branched fluoroalkyl group having at least onefluorine atom. A greater number of fluorine atoms is more preferable. Rfis preferably a C₁₋₁₈ linear or branched perfluoroalkyl group such as(CF₂),CF₃ (wherein n is an integer of 0 to 17), perfluoroisopropyl,perfluoroisobutyl or perfluoro-t-butyl, more preferably C₂₋₁₈perfluoroalkyl.

In the three-step reaction of the invention, it is important to maintainthe reaction system under neutral or basic conditions not only duringthe reaction but also during the post-treatment because the oxetane ringis cleaved under acidic conditions, resulting in a failure to providethe desired compound.

The invention makes a variety of fluorinated alkane iodides availableand thus enables the production of oxetane compounds having the desiredfluorine-containing substituent on the side chain.

The starting compound of the invention,3-alkyl-3-(allyloxy)methyloxetane (1), can easily be prepared by knownmethods, such as a method for synthesizing3-(allyloxy)methyl-3-methyloxetane from 3-methyl-3-oxetanemethanol (J.Macromol. Sci.-Pure Appl. Chem. 2335, A34(1997)) and a method forsynthesizing 3-(allyloxy)methyl-3-methyloxetane from2-(allyloxy)methyl-2-methyl-1,3-propanediol (U.S. Pat. No. 2,924,607).

[Reaction Conditions for Step A]

In order to produce 3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane(I), the inventors used 3-alkyl-3-(allyloxy)methyloxetane (1) as astarting compound and tried to carry out an addition reaction in thepresence of a radical initiator to add perfluoroalkyl iodide. As aresult, it was found that this reaction proceeds to produce the desiredproduct in good yield. Although the addition reaction of perfluoroalkyliodide to an olefin in the presence of a radical initiator was awell-known reaction (general description: J. Fluorine Chem. 1, 93(1999)), the addition of perfluoroalkyl iodide to3-alkyl-3-(allyloxy)methyloxetane was unknown. In this additionreaction, avoiding the cleavage of the oxetane ring is important toproduce the desired product in good yield. For this reason, a reactionunder acidic conditions is not desirable. Since hydrogen iodide isreadily removed from the resulting3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane under basicconditions, basic conditions are not preferable except in the case thatit is desired to obtain compound (II) immediately after the radicaladdition.

In the radical addition reaction, radical initiators such asazobisisobutyronitrile, benzoyl peroxide and t-butyl 2-ethylperhexanoatecan be used or the reaction can be carried out by radical cleavage ofperfluoroalkyl iodide caused by irradiation with light such as by a highpressure mercury lamp.

Although RfI can be reacted with 3-alkyl-3-(allyloxy)methyloxetane (1)in any molar ratio, it is preferable that Rfl be used in an amount of 1to 5 moles per mole of 3-alkyl-3-(allyloxy)methyloxetane (1). Althoughthe amount of radical initiator used may vary depending on the kind ofinitiator, it is usually preferable that the initiator be used in anamount of 1 to 5 mole % relative to 3-alkyl-3-(allyloxy)methyloxetane(1).

The reaction temperature is in the range of about 50° C. to 80° C. andthe reaction time is about 1 to 6 hours. The reaction can be performedin a solvent, for example, ethers such as diethyl ether andtetrahydrofuran, esters such as ethyl acetate, or aromatic hydrocarbonssuch as benzene and toluene.

[Reaction Conditions for Step B]

Next, a reaction to remove hydrogen iodide from3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I) proceedsreadily under basic conditions to produce3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane (II). In this reaction,any appropriate base can be used. Basic conditions which are too strong,however, are not preferable because the reaction further proceeds toremove hydrogen fluoride from3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane, giving a byproduct.Examples of useful bases include alkali metal hydroxides such as sodiumhydroxide and potassium hydroxide, and alkali metal carbonates orhydrogencarbonates such as sodium carbonate, potassium carbonate, sodiumhydrogencarbonate and potassium hydrogencarbonate. The base ispreferably used in an amount of about 1 to 2 moles per mole of thestarting 3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I). Thereaction is preferably carried out at about room temperature and thereaction time is about 0.5 to 2 hours.

[Reaction Conditions for Step C]

Next, 3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane (II) is readilyconverted into 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane (III) inthe presence of a hydrogenation catalyst. Examples of usefulhydrogenation catalysts include palladium/carbon powder,palladium/barium sulfate, platinum oxide and Raney nickel. The catalystcan be used, for example, in an amount of about 0.1 to 5 mass %,relative to the compound (II). Although the reaction proceedssatisfactorily at room temperature and atmospheric pressure, it is alsopossible to carry out the reaction with heating or under pressure. Thereaction time is about 1 to 8 hours. Since reductive cleavage of theoxetane ring may occur under highly reductive conditions, the reactionshould be carried out under conditions under which the oxetane ring isnot cleaved. Examples of useful solvents include ethers such astetrahydrofuran and dioxane, and alcohols such as methanol and ethanol.

[Reaction Conditions for Step D]

Another method for producing3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane (III) comprises reducing3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I) withoutperforming the reaction to remove hydrogen iodide. Such reductionmethods include hydrogenation using a reduction catalyst such aspalladium/carbon powder, palladium/barium sulfate, platinum oxide orRaney nickel, or methods using a chemical reducing agent such astributyltin hydride or lithium aluminum hydride. The reduction catalystcan be used, for example, in an amount of about 0.1 to 5 mass % relativeto compound (I). The chemical reducing agent can be used, for example,in an amount of about 25 to 200 mole % relative to compound (I). Thereaction temperature is in the range of about −78° C. to 40° C. and thereaction time is about 1 to 4 hours. The reaction can be carried out ina solvent such as tetrahydrofuran, dioxane or like ethers.

The compounds of formulas (I), (II) and (III) prepared by the productionprocess of the invention are useful as intermediates for preparingvarious fluorine-containing functional materials, such as resins andcoating surface modifiers.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples are given below to illustrate the invention in more detail, butit is to be understood that the invention is not limited thereto.

In the Examples, 3 m stainless steel columns packed with SE-30 were usedin gas chromatography analysis, unless otherwise specified. NMR wasmeasured with a Bruker 300 MHz spectrometer using chloroform-dl as asolvent.

REFERENCE EXAMPLE 1

Synthesis of 3-(allyloxy)methyl-3-methyloxetane

3-methyl-3-oxetane methanol (20.4 g), 50% aqueous sodium hydroxidesolution (268 g), tetrabutylammonium chloride (2.8 g) and hexane (300ml) were placed into a 500 ml flask and stirred at room temperature.After 19.4 g of allyl bromide was added dropwise, the reaction mixturewas heated and refluxed for 2 hours. After completion of the reaction,the reaction mixture was filtered and separated into aqueous and organicphases. The aqueous phase was extracted with ethyl acetate and theextract was combined with the organic phase and washed with water. Thesolvent was distilled off using an evaporator, giving 17.2 g (61%) ofproduct. The product was analyzed by gas chromatography and the resultsshowed that the desired 3-(allyloxy)methyl-3-methyloxetane was obtainedin a purity of 98%. Therefore, the product was used without purificationfor the following reaction.

¹H-NMR: 1.31(s,3H), 3.50(s,2H), 4.00(d,2H), 4.33(d,2H), 4.50(d,2H),5.17(d,1H), 5.27(d,iH), 5.92(m,1H)

EXAMPLE 1

Radical Addition

3-(allyloxy)methyl-3-methyloxetan (7.1 g), nonafluorobutyl iodide (51.9g) and azobisisobutyronitrile (0.245 g) were placed into a 100 ml flaskand stirred at room temperature. Then the reaction mixture was heated to70° C. and maintained at that temperature for 1 hour.

After completion of the reaction, nonafluorobutyl iodide was distilledoff using an evaporator, giving 22.2 g of product. The product wasanalyzed by gas chromatography and the results showed that the desired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-iodoheptyloxy)methyl-3-methyloxetanewas obtained in a purity of 94%. Yield: 85%.

¹H-NMR 1.33(s,3H), 2.88(m,2H), 3.59(s,2H), 3.74(m,2H), 4.38(d,2H),4.41(m,1H), 4.52(d,2H)

¹⁹F-NMR −81.6 ppm(3F), −114.4(2F), −125.1(2F), −126.4(2F)

EXAMPLE 2

Removal of Hydrogen Iodide

3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-iodoheptoxy)methyl-3-methyloxetane(19.5 g) was placed into a 100 ml flask and stirred at room temperature.Then 25 ml of a methanol solution containing 4.2 g of potassiumhydroxide was added dropwise and stirred overnight. The reaction mixturewas filtered and washed with aqueous sodium thiosulfate solution andwater and then dried over magnesium sulfate. The obtained product (8.5g) was analyzed by gas chromatography and the results showed that thedesired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptenyloxy)methyl-3-methyloxetane wasobtained in a purity of 93%. Yield: 59%.

The desired compound was obtained as a separable 78:22 (E:Z) mixture ofgeometric isomers. This mixture was separated by HPLC under thefollowing conditions:

HPLC Conditions

Column: Fluofix 120N (Φ4.6*150 mm, product of Neos Co., Ltd.)

Mobile phase: Acetonitrile/water

Detection: UV(210 nm)

E-isomer

¹H-NMR 1.27(s,3H), 3.50(s,2H), 4.14(m,2H), 4.33(d,2H), 4.46(d,2H),5.87(dt,1H), 6.43(m,1H)

¹⁹F-NMR −82.1 ppm(3F), −112.8(2F), −125.2(2F), −126.7(2F)

Z-isomer

¹H-NMR 1.25(s,3H), 3.46(s,2H), 4.28(m,2H), 4.33(d,2H), 4.46(d,2H),5.55(dt,1H), 6.26(m,1H)

¹⁹F-NMR −82.1 ppm(3F), −112.8(2F), −125.5(2F), −126.7(2F)

EXAMPLE 3

Hydrogenation

3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptenyloxy)methyl-3-methyloxetane(7.2 g) and 5% palladium/carbon powder were placed into a 100 ml flaskand stirred at room temperature. After the flask was purged withnitrogen, hydrogen was circulated through the flask at about 60 ml/minfor 4 hours. Then the reaction mixture was filtered through a celitecolumn to remove the hydrogenation catalyst from the reaction solution.The obtained product (7.0 g) was analyzed by NMR and the results showedthat the desired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptyloxy)methyl-3-methyloxetane wasobtained in a purity of 95%. Yield: 95%.

¹H-NMR 1.33(s,3H), 1.78(m,2H), 2.19(m,2H), 3.50(m,2H), 3.59(s,2H),4.38(d,2H), 4.52(d,2H)

¹⁹F-NMR 81.6 ppm(3F), −114.4(2F), −125.1(2F), −126.4(2F)

INDUSTRIAL APPLICABILITY

According to the invention, the known compound3-alkyl-3-(allyloxy)methyloxetane is used as a starting compound and aradical addition reaction is carried out to add fluorinated alkaneiodide, thus giving3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, which is animportant intermediate for oxetane compounds having afluorine-containing substituent at the 3-position. Further,3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane can be convertedunder basic conditions into3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane, which can further beconverted into 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane through areduction reaction.

What is claimed is:
 1. A process for preparing a compound of formula (I)comprising radical addition of RfI to 3-(allyloxy)methyl-3-alkyloxetane(1) wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branchedfluoroalkyl,


2. A process for preparing a compound of formula (II) comprisingreacting the compound of formula (I) under basic conditions to removehydrogen iodide therefrom wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linearor branched fluoroalkyl,


3. A process for preparing a compound of formula (III) comprisinghydrogenating the compound of formula (II) in the presence of ahydrogenation catalyst wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear orbranched fluoroalkyl,


4. A process for preparing a compound of formula (III) comprisingreducing the compound of formula (I) in the presence of a reductioncatalyst or a reducing agent

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.5. A compound of the formula (I)

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.6. A compound of the formula (II)

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.